Variable throw eccentric mechanism



Dec. 27, 1932.

F. L. DAVIS,r .1R

VARIABLE THROW ECCENTRIC MECHANISM Filed OCt. 18 1929 2. Sheets-Sheet 1 Dec. 27, 1932.

F. l.. DAvls, JR 1,892,504

VARIABLE THROW ECCENTRIC MEGHANISM Filed ont. 18. 1929 2 sheets-sheet 2 ATTORN EYS Patented Dec. 27, 1932 UNITED STATES PATENT OFFICE FRANK L. DAVIS. JB., OF KENILWOBTH, NEW JERSEY, ASSIGNOR TO THE WATSON- STILLIAN C0., OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY VARIABLE THROW ECCENTRIG MECHANISM Application led IOctober 18, 1929. Serial No. 400,599.

Important objects of the present invention are, to providepan improved driving mechanism for a plunger pump, capable of adjustment to vary the plunger stroke in accordance with diii'erent fluid pressure requirements; to provide for varying the stroke of the pump plunger while the pump is operat ing; to provide for automatically varying the stroke through means operated by fluid pressure developed by the pump; and to provide an eccentric mechanism including means for automatically varying the eccentric throw.

In the drawings:

Fig. 1 is a side view of a hydraulic power driven pump embodying the invention;

Fig. 2 a longitudinal section taken through the adjustable eccentric mechanism; j

Fig. 3 a section taken on the line 3 3 of Fig. 1;

Fig. 4 a section taken on the line 4--4 of Fig. 1;

Fig. 5 a view similar to Fig. 2 showing another adjustment of the eccentrics;

Fig. 6 a transverse section taken on the line 6 6 of Fig. 5

Fig. 7a detail sectional view of a valve device in the fluid connection between the pump and the eccentric adjusting mechanism;`

Fig. 8 a detail face view of one of the eccentric disks;

Fig. 9 a detail plan view of a portion of the eccentric drive shaft with the eccentric mountings formed thereon;

Fig. 10 a perspective view of the portion of the drive shaft shown in Fig. 9 together with the integral eccentric mountings and one of the eccentric thrust connections detached;

Fig. 11 a section taken on the line 11--11 of Fig. 6; and

Fig. 12 a section of Fig. 10. A

The invention is directed particularly to an improvement in power driven hydrauflic plunger pumps of the type employed or operating hydraulic presses. It has been the custom heretofore to operate hydraulic presses by means of pumps whose driving means are unprovided with any means for varying the plunger stroke in accordance taken on the line 12-12 high pressure pump is operating the low Apressure pump yis cut out. There are no presv sure gradations between the ressure capacities of said pumps correspon ing to the gradual increase of the ram resistance.

The present invention provides for the satisfactory operation of a hydraulic press by v a single pump which is so operated as to vary the plunger .stroke accurately iny accordance with variations in the ram resistance. This is accomplished automatically while the pump is running. 'From the single pump, with a constant power input, a fluid delivery is obtained, varying within the limits of the pump capacity, from a large volume at low pressure to a small volume at high Y pressure. Thereby the ram -is'moved rapidly when under no load, and when a load is imposed the pressure is automatically increased to the required degree.

The invention is illustrated as applied to a two plunger pump. Without changing the principle of the invention,'however, it may be readil designed for a pump having any reasonab e number of plungers, from one upward. The pump proper, designated 1 is mounted upon a base 2between two bearing pedestals 3 and 4. Base 2 is mounted upon a box-like tank 5 which contains the fluid supply and has a fluid connection, not shown, with the pump intake. The pump is of a standard design and illustration of its interior structure is therefore omitted.

Two split bearings 6 and 7 are supported in horizontal alinement by the pedestals 3 and 4 respectively and rotatably support the improved driving mechanism for the pump. Said mechanism includes a drive shaft 8 extending through and beyond both bearings. This shaft is of tubular form. Upon its end portion projecting from bearing 4 two belt pulleys 9 and 10 are mounted. Pulley 9 1s a drive pulley and is keyedto the shaft at 11. Pulley 10 is a loose ulley freely rotatable upon the shaft and) held 1n place by a collar 12 fastened to the shaft. A collar 13 is fastened to the opposite end portion of the shaft to abut bearing 6 and prevent endwise displacement of the shaft.

Between the bearings 6 and 7 the shaft is formed with a slightly enlarged squared portion 14, and formed with said squared portion, at the opposite ends thereof, are two radial extensions 15 and 16 also squared and extending in opposite directions. These squared extensions are slightly spaced apart along the shaft and form mountings for two adjustable eccentric disks 17 and 18.l Said disks are of the same size and form. Each is circular and is formed with a rectangular opening 19 truly centered and proportioned to receive the squared portion of the shaft, together with one of its squared radial extensions. The eccentric mounting formed by said shaft parts has flat opposite sides 20 and the longer sides 21 of said rectangular opening in the eccentric disk are flat and slidably engage the sides 20. The disk opening its somewhat longer than the mounting therein so that the disk is mounted to shift transversely ofthe shaft to vary its eccentricity but is held to rotate with the shaft.

A central shaft 22 is fitted for longitudinal sliding within the tubular drive shaft 8 and extends entirely through the latter and beyond the ends thereof. This shaft 22 forms part of the means for adjusting the eccentric disks to vary their eccentricit Near one end, the shaft is formed with a ey Yslot 23 into which projects a set screw 24 threaded into the collar 13 and extending through an aperture in the shaft 8. Thereby, the adjusting shaft 22 isilocked to rotate with the drive shaft 8 but is free to slide longitudinally through the latter. The medial p01'- tion of shaft 22 is formed to provide two straight sloping cam faces 25 and 26 for shiftingvthe eccentric disks 17 and 18 respectively to vary their throw. The cam faces are formed by sloping cut-outs in the shaft. They are of the same size and shape but are located at opposite sides of the shaft and spaced therealong tol bring them into proper relation to their respective disks. Their slopes extend in the same longitudinal direction but in opposite transverse directions, and at their low points they merge with curved ends 27 of the cut outs.

Between each of said cam faces'and the ec- 'centric disk which it is intended to adjust slidabl fitted in a radial bore 29 extendin throu the respective squared extension o the tu ular drive shaft and opening into the interior of the shaft. At its outer end the block 28 abuts the adjacent end face of the opening 19 of the eccentric disk. Here it is end, within the bore 29, the block is forked and rotatably supports a roller 31 for enga ing the respective cam face. When the a justing shaft22 is shifted in one direction,that 1s toward the left with reference to Figs. 2 and 5 of the drawings, the two thrust connections are cammed radially outward in opposite directions and the'eccentric disks 17 and 18 are shifted thereby in unison and to the samev degree to increase their throw.

When the adjusting shaft 22 is shifted toward the ri ht with reference to Figs. 2 and 5, the cam ces are moved to provide clearance for inward movement of the thrust connections and thereby permit shifting of the eccentrices to reduce their throw. This shifting of the eccentric disks is done auto matically by compression springs 32. In the present instance there are four of. these springs for each eccentric disk, disposed in bores 33 formed in the eccentric mountin These bores are arranged around the gui e bore 29 for the thrust block but open outl' sure tending to re uce the eccentric t row l and they are of suicient strength to hold each thrust roller 31 firmly against its cam face and maintain a given eccentric throw throughout all phases f the eccentric move ment.

The eccentric 17 and 18 are operatively connected to the pump plungers in the usual manner. A sectional strap 34 encircles each disk and is provided with a downwardly extending arm 35 pivotally connected to a cylindrical crosshead 36. The cross heads are mounted for vertical sliding in cylindrical guides 37 which are formed with a web 38 extending between the bearing pedestals 3. Between the crossheads and the pump plungers are driving connections 39.

A fluid pressure o rated mechanism is provided for automatlcally shifting the adjusting shaft 22 and thereby effecting adjustments of the eccentric throw in accordance with varying preure requirements. A bracket 40 is secured to or formed upon one side of the bearing pedestal 3 to support said mechanism. Included in the mechanism is a cylindrical casing member 41 formed with held to the disk by a screw 30. At its inner roo a reduced threaded end 42 which is vertically screwed into a threaded opening in a shelf formed by said bracket. The cylinder 41 is formed with an axial bore 43 opening through its lower end and closed at its upper end. Slidablyfitted in said bore is aplunger44 having a flexible, concave washer 45 upon its upper end to form a leak-proof fit. A fluid pressure chamber is thereby defined in the c linder, above the plunger. Connected to t e cylinder and opening into the upper end of said chamber is a sectional pipe 46 which extends downwardly and is connected to the casing of the pump 1 to communicate with the delivery chamber or port of the pump. A valve casing 47 is tapped into the pipe and contains an upwardly opening check valve 48 a by-pass 49 extending around the check valve, and a manually operable needle valve 50 to regulate a flow through said by-pass. The pipe conducts fluid under pressure from the pump delivery to said pressure chamber 43 for depressing the plunger 44.

At its lower end plunger 44 is provided with a long vertical stem 51 whose lower end passes through a bore formed in a threaded plug 52 and is guided thereby. Plug 52 is screwed upwardly through an aperture in a supporting shelf formed upon the lower end of bracket 40 and is formed with a reduced, squared lower end 53 for turning it. A collar 54 is fixed upon the stem 51 and between said collar and the plug 52 is interposed a strong compression spring 55 encircling the stem. This spring constantly opposes depression of the plunger 44 by the fluid pressure. Between the collar 54 and the adjusting shaft 22 there is an operative connection which includes a lever 56. The latter is formed with a sleeve-like fulcrum portion 57 which is pivoted as at 58 between two ears formed upon the bracket 40. From said fulcrum portion extends a pair of short lateral arms 59 which straddle the collar and are operatively connected thereto as at 60 for rocking the lever, when the plunger is shifted. The lever has a long arm 61 extending upwardly from the fulcrum and formed with ah inverted U-shaped yoke. portion which straddles the shaft 22. Fixed to the latter is a grooved collar 62 and the lever yoke is operatively connected as at 63 with opposite sides of the collar for shifting the shaft longitudinally. At its upper end the lever is formed for manual operation when required.

The opposite end of the shaft 22 from said lever connection is reduced and threaded as at 64 and has a nut 65 and lock nut-66 screwed upon it. The nut is adapted to abut the collar 12-fixed to the shaft 8 and serve as an adjustable stop to limit the movement of adjusting shaft 22 toward the left, with reference to Figs.. 2 and 5. Since movement of the shaft in this direction increases web 69 extending across the lever yoke and is adapted to contact the bracket 40 and limit the throw of the lever accordingto the adjustment. A lock nut 70 is screwed upon the screw vto maintain the adjustments of the latter. Since movement of the shaft 22 toward the right reduces the eccentric throw the limit of said reduction will be determined by the adjustment of screw 68.

In the use of the pump with the improved adjustable driving mechanism, the various adjustments are first made in accordance with the needs of the service. Assuming for example that the pump is to operate a hyf' draulic press, the pressure of spring 55 is adjusted by turning the threaded plug 52; the stop nut 65 upon the adjusting shaft 22 is adjusted to limit the maximum eccentric throw and the stop screw 68 upon the lever is adjusted to limit the minimum eccentric throw. The adjustment of spring 55 is made in accordance with the relatively low pressure required for moving the press ram upon its preliminary stroke when the resistance is slight. Then, when the pump is operated by rotating the belt pulley 9, drive shaft 8 fat and the eccentrics, the low pressure will develop in the pump delivery, and fluid under said pressure will flow through the pipe 46, past the check valve 48, to the compression cylinder 41, where it will tendto depress the plunger 44 and, through the o erative connection of the plunger with adjusting shaft 22, tend to shift the latter to the right for a reduction of the eccentric throw. This low pressure is, however, resisted by sprlng 55 which prevents depression of the plunger and thereby maintains the maximum eccentric throw within the limits of the adjustment. Consequently there is amaximum fluid delivery from the pump to the press for rapid movement of the ram.

As the movement of the press ram progresses and it encounters resistance, the pressure in the pump delivery builds up and 1s transmitted through pipe 46 to the compression cylinder. When the pressure increase is sufficient to overcome the resistance of spring 55 theplunger is depressed and4 the lever is rocked in a direction to shift the adjusting shaft toward `the right for a reduction in the eccentric throw. The reduction increases the mechanical advantage ofv the driving force and accords accurately with the inros crease of fluid pressure over the spring resistance. As the ram resistance increases, the eccentric throw is further reduced automatically to a sufficient degree to overcome the resistance. In theory, infinite gradations of pressure are obtainable by this automatic means in accordance with the needs of the press or other driven device.

The check valve 48 prevents an undesired drop of pressure in the compression cylinder 41 during phases of the pump strokes when the pressure is momentarily relaxed or reduced. The by-pass 49 however provides for a return of fluid to the pump delivery at a rate properly regulated by the valve 50 to relieve the pressure upon the plunger 44.

While I have shown and described a satisfactory form of my invention and an advantageous use thereof, I do not wish to be limited strictly to this disclosure but reserve the right to make such changes in structure and use as will lie within the scope of the claims.

What I claim is:

1. An eccentric mechanism comprising a tubular shaft; an eccentric held to rotate with said shaft and mounted to shift transversely thereof to vary its eccentricity; an adjusting member mounted to shift longitudinally in said shaft and bearing a transversely directed cam face; a thrust connection between said cam face and the eccentric for shifting the latter to increase its throw when the adjusting member is shifted in one direction; spring means tending' constantly to shift the adjusting member in said direction; spring means to resist said shifting of the eccentric, tendin constantly to reduce the eccentric throw; uid pressure operated means to shift the adjusting member in the reverse direction to relieve the cam pressure and permit said second spring means to reduce the eccentric throw; and adjusting means to vary the force of said first spring means acting upon the adjusting member.

2. An eccentric mechanism comprising a tubular shaft; an eccentric held to rotate with said shaft and mounted to shift transversely thereof to vary its eccentricity; an adjusting member mounted to shift longitudinally in said shaft and bearing a transversely directed cam face; a thrust connection between said cam face and the eccentric for shifting the latter to increase its throw when the adjusting member is shifted in one direction; spring means tending constantly to shift the adjusting member in said direction; spring means to resist said shfting of the eccentric, tending constantly to reduce the eccentric throw; means to shift the adjusting member in the reverse direction torelieve the cam pressure and permit said second spring first spring means acting upon the adjusting member.

3. An eccentric mechanism comprising a tubular shaft; an eccentric held to rotate with said shaft and mounted to shift transversely thereof to vary its eccentricity; an'

adjusting member mounted'to shift ngitudinally in said shaft and bearing a transond spring means to reduce the eccentric throw.

In testimony vwhereof I hereunto aix my signature.

FRANK L. DAVIS, JR. 

